chore(Dropdown): update examples to show different appends

[thatblindgeye]

What: Closes #6824

Similar to PR #7087, this does not resolve the issue with appending to document.body, but rather cautions against it and provides the alternative of appending to "parent". Appending to "parent" should offer the same benefits of document.body, but also allow assistive technologies to navigate into the component's contents and also keep things in a more proper DOM order.

I also created another codesandbox to show both variants being used inside of a Modal: Dropdown appended inside Modal. This shows the similarity between them when opened inside a Modal, and also the difference if using Voice Over to try and navigate inside the Dropdown contents.

Additional issues:

[patternfly-build]

Preview: https://patternfly-react-pr-7095.surge.sh

A11y report: https://patternfly-react-pr-7095-a11y.surge.sh

[nicolethoen]

I think you should move the instructional text to the relevant example below. It's great information, but probably does not need to be the very first piece of information on the Dropdown page.

And just like the Select PR you also have open - I wonder what @mcarrano and @tlabaj would say about having an anti-example in the docs, even if it's a powerful instructive demonstration.

I think that I like it, personally.

[thatblindgeye]

In addition to moving the verbiage I also added a quick explanation of what the differences between the two examples here are to match how I have the Select example description. That's easy enough to remove that + the anti-examples if that ends up being way to go, though.

[jessiehuff]

I like the verbiage. 🙂

[mcarrano]

I like it, too!